My solana is 2-1/2 months old and the skimmer wasnt working like it should, there wasnt any real skimmate produced in the last weeks.
Some times it just stopped producing bubbles, I had to turn the pump on and off to make it start working again.
Well I got tired of the poor performance from the stock skimmer so I decided to give it a clean, the was some minor debris on the pump, the red bioballs inside where all covered in debris and I cleaned then, the air inlet tube was clogged with some white looking debris (no wonder why it wasnt working)
After the maintenance the skimmer started working good again.... I will always clean the skimmer from now on when I do my waterchanges...